Cross Reference to Related Application

This is a continuation-in-part of U.S. Application 20701, Serial Number 07/364,793 filed on June 9, 1989.

Background of the Invention

Nonimpact printing is performed by application of a toner or other print medium, collectively referred to hereinafter as "toner," to a substrate such as by ion deposition printers, laser printers, Xerox brand type printers, ink jet printers and thermal transfer printers. A wide variety of substrates are used with such printing such as paper, plastics and vinyl.

The adhesion of the toner to such substrates is not entirely satisfactory. During normal handling, abrasions to the toner printed on substrates will cause portions to come loose, particularly toner printed with ion deposition printers where the toner is only pressure fused to the substrate. Laser printers and Xerox brand type printers provide for a little better adhesion because they fuse the toner to the substrate by pressure and heat.

A need exists to improve such adhesion and to make toners abrasion resistant. These objectives are the subject of the instant invention.

Summary of the Invention

It has been found that improved toner adhesion and resistance from abrasion can be achieved, particularly for toners fused by pressure alone at room temperature. This improved adhesion is achieved by applying to the printing substrate a polymeric film forming material suitable for forming a print-receptive coating which when cured or dried will have a dynamic storage tensile modulus ranging from about .01 x 10 9 to about 26 x 109 dynes per square centimeter when measured on a Rheometriσs Mechanical Spectrometer, model 800, at 25 ^β C at a frequency of 10 radians per second using the film fixture attachment. At this modulus range the coating will be soft enough to deform and accept the toner without undue smearing and without allowing the toner to come loose from the coating during normal handling, but without being so soft as to cause one sheet of paper to adhere to the next or jam when contacted by rollers in a printing machine.

While the print receptive coating can be beneficially applie -to a wide variety of substrates, the preferred substrate will be a compressible substrate with the most preferred a porous, compressible substrate such as paper or a pressure sensitive label construction.

Virtually any polymeric film forming material may be used as a coating, provided that it is suitable for forming a print-receptive coating and has a modulus range as specified above, when cured or dried.

The polymeric film forming materials used to form the coating of the present invention may be prepared and applied to the substrate and cured or dried thereon using water based emulsions or organic solvent systems, or using 100% solids reactive systems which are cured by ultraviolet (UV) or electron beam radiation before transfer of the toner. The coating viscosity of the print receptive coating should be high enough to prevent undue soak into the most preferred porous substrate.

The coatings have utility as a surface for single cut sheets or for label face stock. They are particularly useful for printed bar codes in preventing the contact bar code reader from abrading off the bar code image and making the bar code unreadable.

Particular polymeric materials suitable for use in forming coatings of the 100% solids reactive system of the present invention are acrylated oligomers and mixtures therefore, and oligomers selected from the group consisting of acrylated urethane oligomers, acrylated epoxy oligomers and polyacrylic oligomers.

Preferred Embodiments

Exemplary formulations of polymeric materials suitable for forming print-receptive coating are set forth in Table I below.

TABLE I

Formulations in Weight Percent of Total Formation

Ebecryl 4833

(Acrylated Urethane Oligomer) 21.6 75.7 — 21.6 37.85 54.1 37.85

Ebecryl 769

(Polyacrylic Oligomer) 54.1 — — — 37.85 21.6 — 37.85 75.

Ebecryl 4883

(Urethane Acrylate Oligomer — — — 54.1

Aerylate Monomer Blend)

CMD-3703

(Acrylated Epoxy Oligomer) — — ^' 75.7 — — — 37.85 37.85 —

N-Viny1-2-Pyrrolidone

(reactive diluent) 17.4 17.4 17.4 17.4 17.4 17.4 17.4 17.4 17.

2,2-diethoxyacetophenone

(U.V. sensitizer) 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.

Z-6040 (coupling agent) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.

100. 0 100. 0 100. 0 100. 0 100. 0 100.0 100. 0 100. 0 100.

Formulation 10 9 Parts Formulation #1 and 1 Part of a silica flatting agent OK412

Formulation 11 Joncryl 80 Acrylic Emulsion

Formulation 12 Rhoplex 1533 Acrylic Emulsion

The dynamic storage tensile modulus, E ¹ , the dynamic tensile loss modulus E", and the loss tangent (tan d = E"/E') , of each formulation of Table I is set forth in Table Iϊ below wherein each cured formulation is ranked as its modulus increases from the softest coating, No. 12, to the hardest coating, No. 7.

Table II also sets forth the modulus of each formulation using a frequency of 10 and 100 Radians per second for the sake of comparison. It is believed that the time of 0.1 sec (corresponding to a frequency of 10 radians/sec) approximates the time that pressure is applied to any given toner particle during the fusing operation and that the coating modulus at that frequency is the important parameter for determining toner adhesion and abrasion resistance.

Ultraviolet curable coatings applied to a 20 pound per ream ion deposition grade bond paper manufactured by Boise Cascade Co. were cured with two 300 watt per inch medium pressure mercury vapor UV lamps. The coating viscosity at application ranged from 350-2500 cps. as measured by a Brookfield viscometer with a number 6 spindle at 100 RPM. Under these conditions, good surface coatings were provided onto the surface with no detrimental penetration into the porous sheet. Line speed was 70 feet/minute with the application to drying distance of 24 inches, giving a time to cure of 1.7 sec. All coatings had a surface energy greater than 30 dynes/cm 2.

The ultraviolet curable coatings were applied by flexographic techniques, but other coating techniques known in the art may be utilized. The required weight of the coatings are from 0.5 to 5 grams/meter 2.

Table :El

E'(§ E' (§ E' » (@ E' » (@ tan Z(@ tan Z(l 10R/S) 100R/S) 10R/S) lOOR/S) 10R/S) IOOR/S; XlO ³ XlO ⁹ XlO XlO ⁹

Formu¬ Dynes/ Dynes/ Dynes/ Dynes/ lation cm cm cm c

12 0.3 1.2 0.33 1.16 1.10 0.97

9 0.9 1.0 0.28 0.40 0.31 0.40

11 2.2 2.5 0.24 0.23 0.11 0.09

1 5.9 9.1 1.89 2.36 0.32 0.26

5 6.2 9.1 1.72 2.21 0.28 0.24

10 7.6 10.7 2.20 2.68 0.29 0.25

6 8.5 11.2 1.79 1.95 0.21 0.17

4 8.7 11.1 1.53 1.63 0.18 0.15

8 10.2 13.0 1.50 1.96 0.15 0.15

2 14.1 17.0 1.93 1.90 0.14 0.11

3 21.2 22.4 0.74 0.85 0.04 0.04

7 25.9 28.6 2.10 2.17 0.08 0.08

Table III sets forth measurements of how well toner adheres to the coatings of the present invention. The coatings were applied to 20 pound bond paper as aforesaid.

The toner was printed on said coated paper by fusing the toner thereon by pressure alone by a C. Itoh electronics model Megaline/30 printer using a Delphax engine S-3000 operating at room temperature using an alpha numeric test pattern as the image. No transport problems were experienced through this multiroll machine indicating excellent performance against jamming or blocking. The toner was Delphax Monocomponent Ion Deposition toner manufactured by Coates Special Products, Kent, England. An adhesive tape (Scotch 610) was applied to toner printed on a sheet of uncoated paper (the control) and to toner printed on eight sheets of coated paper having eight different coating formulations as set forth in Table I, with the results tabulated in Table III. The adhesive

tape removed most of the toner from the uncoated paper but did not remove enough toner from the paper having coating formulations 1 to 8 to adversely affect their readability.

The amount of toner removed as aforesaid is measured in terms of its readability which is measured by a PCM II instrument manufactured by MacBeth Company. The PCM II instrument measures readability in terms of the print contrast, i.e., the reflectivity of the printed image relative to the reflectivity of the paper, to give print contrast readings as set forth in Table III and IV. Print contrast readings are reported in Tables III and IV as 100 times the decimal reading of the instrument, i.e., as a percentage figure. The PCM II has a 0.008 inch reading diameter. The measurements were an average of 5 to 7 readings taken at the intersection of the horizontal and vertical sections of letters such as "B" and "E". Print contrast readings of 70% or above are generally readable.

The Print Contrast measurements set forth in Tables

III an IV were made with the PCM II instrument using a "C" filter with a 3050 K source. The "C" filter has a response range of from about 639 nm to about 1110 nm and a central peak response at 800 nm wavelength.

Table III

Print Contrast Reading of Sheets Imaged by E ¹ x 10 in Dynes/cm Ion Deposition (%) at 25 " C

Paper Paper Sheet θ 10 § 100 Sheet After Partial

Formu¬ Radians/ Radians/ with Removal of lation Second Second Toner Toner with Tape

Control

(paper wwiitthh nnoo 9955..99 15.6 coating)

1 5.9 9.1 95.8 94.5

5 6.2 9.1 96.8 95.1

6 8.5 11.2 96.4 94.5

44 88..77 1111..11 9955..99 88.6

8 10.2 13.0 96.6 89.3

2 14.1 17.0 95.6 93.0

3 21.2 22.4 96.5 70.5

7 25.9 28.6 96.0 86.8

Table IV sets forth measurements made with the PCM II using a different alphanumeric test pattern as the image.

Table IV

Print Contrast Print Contrast

Reading Before Reading After

Formulation Tape (%) Tape (%)

Uncoated Paper (Control) 93 56

1 94 91

2 94 90

6 94 89

7 94 89

8 93 88

9 93 87

10 93 89

11 95 90

12 94 88

Ebecryl 4833 is the trade name of an acrylated urethane oligomer used in the present invention, and is marketed by Radcure Specialties of Norfolk, Virginia. Ebecryl 4833 is prepared by reacting a isocyanide with a polyester polyol to obtain a urethane backbone which is reacted with acrylic acid to produce an acrylated urethane oligomer. The acrylated urethane oligomer used in the present invention has a molecular weight of about 1,500, and functionality of 2. This oligomer constitutes about 90% by weight of solids, the remainder being a diluting reactive monomer, N-vinyl-2-pyrrolidone. This oligomer, including the diluting monomer, has an acid number between 0-3, a color between 1-3, and a viscosity in centerpoise of 1670-2670 at 140 ^β F and 775-1175 at 160°F. The weight per gallon is 9.2 - 9.4 pounds.

Ebecryl 769 is the trade name of a polyacrylic oligomer used in the present invention, and is sold by Radcure Specialties of Norfolk, Virginia. Ebecryl 769 is a blend comprising about 74% by weight of polyacrylic oligomer, about 26% by weight of isobornyl acrylate. This blend has the following characteristics: A specific gravity of 1.06, a vapor pressure of less than 0.1 in millimeters of mercury, a volatility of less than 0.3 by weight, an evaporation rate of less than 1, with the evaporation rate of butyl acetate being 1, and a lack of solubility in water.

Ebecryl 4883 used in the present invention is a blend of about 85% by weight of urethane acrylate oligomer and about 15% by weight of an acrylate monomer tripropylene glycol diacrylate. It is sold by Radcure, Inc. of Port Washington, Wisconsin. This blend has a vapor pressure of less than 0.1 millimeters of mercur ^' , a molecular weight of about 1500, a specific gravity of about 1.10, a volatility of less than 0.3 by weight, and an evaporation rate of less than 1, with the evaporation of butyl acetate being 1.

CMD 3703 used in the present invention is the trade name of an acrylated epoxy oligomer, marketed by Radcure, Inc., as above, and more specifically is a diacrylate ester of an amine-modified bispheonol A type epoxy resin with 5% added hydroxypropyl acrylate. It has a viscosity at 65 ^β C of 2,000 cps., a Gardner color of 3 to 4, an acid value of 3, a theoretical molecular weight of 834 and a theoretical functionality of 2.

A variety of reactive diluents may be used with the present invention, exemplary of which are N-vinyl-2-pyrrolidone; tri ethylolpropanetriacrylate; 1,6 hexanediol diacrylate; diethylene glycol diacrylate and vinyl acetate (not greater than 15%) .

A variety of photoinitiators may be used with the present invention, exemplary of which are 2,2-diethoxyacetophenone, N-methyldiethanolamine and benzophenone, all of which are manufactured by the UpJohn Company of North Haven, Connecticut.

Z6040 is the trade name of silane coupling agent manufactured by Dow Corning Co. of Midland, Michigan, and used with the present invention. It has a specific gravity of 1.070 and a viscosity at 25 ^β C of 3 c St.

Joncryl 80 used in the present invention is the trademark of S.C. Johnson & Son, Inc. of Racine, Wisconsin, for a milky appearing dispersion of an acrylic polymer used for adhesion to polyolefins and foil and having the following physical characteristics: a viscosity of 400 cps, a weight of 8.7 pounds per gallon, and a pH of 8.3. Rhoplex AC - 1533 is the trademark of Rohm & Haas Co. , of Philadelphia, PA, for a hydroxyl functional acrylic emulsion polymer having the following physical properties: a solids content of 46 to 47%, a pH of 8.6 to 9.2, a density of 8.8 lbs/U.S. gal. (wet) and 9.43 lbs/gal. (dry), N,N, - dimenthylaminoethanol, as a neutralizing amine, a minimum film forming temperature of 21°C, and Tukon hardness (KHN) of 6 to 7.

Flatting agent OK 412 is the trademark of the Degussa Company for a finely divided silica having a Si0 ₂ content of 99%, a pH of 6 of a 4% aqueous suspension, a tapped density of 120 g/1, a specific gravity of 1.9, a refractive index of 1.45, and an average particle size of 3 l .

Excess gloss given to the paper from the pressure fusing may be considered detrimental. In that case, suitable amounts of flatting agents such as silica can be added to reduce the gloss of the coating as illustrated in Table V. The measurements of gloss in Table V were made with a Gardner GG - 9095 multi-angle glossmeter. Formulation No. 10 in Table V is identical to formulation No. 1 except for the addition of a silica.

Table V

45° GLOSS 60° GLOSS 75° GLOSS

Before After Before After Before After

Formu¬ Imag- Imag¬ Imag- Imag¬ Imag- Imag¬ lation ing ing ing ing ing ing

Control 6 8 4 7 6 13 No. 1 10 11 10 11 20 24 No. 10 6 7 4 7 7 14

While the embodiments of the invention chosen herein for purposes of the disclosure are at present considered to be preferred, it is to be understood that this invention is intended to cover all changes and modifications in all the disclosed embodiments which fall within the spirit and scope of the invention.